EPA requested the Science Advisory Board provide advice on EPA's Interim Guidance on Environmental Models as well as the development of a models knowledge base. The interim guidance is meant to outline best practices in the development, evaluation and use of environmental models that inform the decision-making process. EPA intends the knowledge base to serve as a web-accessible inventory of environmental models that will promote transparency in the data, algorithms, assumptions, and uncertainties underlying models and enable developers and analysts to more easily identify information needs.